Peak power use with pilot monitoring

ABSTRACT

An aircraft having an electric motor coupled to a rotor and an instrument electronically connected to the electric motor and configured to communicate a time available value before a motor condition reaches a motor condition limit.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.16/054,027, filed Aug. 3, 2018, the contents of which are incorporatedby reference in their entirety herein for all purposes.

BACKGROUND

This section provides background information to facilitate a betterunderstanding of the various aspects of the disclosure. It should beunderstood that the statements in this section of this document are tobe read in this light, and not as admissions of prior art.

Aircraft instrumentation continues to improve as more and more flightinformation becomes available. Terrain elevation data, mapping data,traffic avoidance, and weather information are examples of data that arenow routinely provided to pilots during flight. However, as moreinformation becomes available, information overload has increased. It istherefore desirable to limit the display of information to only what isrelevant at a given moment. Limiting the relayed information hasincreased the need for the pilot's display to be intuitive, since thepilot does experience continuous training through familiarity withinformation that is presented “part-time.”

While many improvements have occurred due to the presentation of flightdata, power management remains relatively unchanged. In the fixed-wingenvironment, the lack of change is understandable, since powermanagement is straightforward, manifesting simply as an ingredient thatadjusts altitude or airspeed.

However, for a rotorcraft, power indication is akin to flightinstrumentation in importance. Understanding power in a rotorcraft isessential to properly manage performance and maintain power situationalawareness. The power required to operate a rotorcraft may substantiallychange during the flight path of the rotorcraft. A rotorcraft requiresfar more power during hover than in any other flight regime.Furthermore, the power required during hover is affected by a variety ofvariables, such as crosswind, air temperature, altitude, and weight.

Statistics reveal that a pilot's loss of situation awareness and theresulting exceedance of aircraft performance restrictions is among thehighest causes of fatal helicopter accidents. “Reported power loss” isalso among the highest causes of fatal helicopter accidents, althoughmany of these are shown to be unsubstantiated, suggesting that perhapsthe pilot did not have a true understanding of how close the powersituation was to the limits of operation or authority.

SUMMARY

An exemplary embodiment of an aircraft includes an electric motorcoupled to a rotor and an instrument electronically connected to theelectric motor and configured to communicate a time available valuebefore a motor condition reaches a critical condition limit, such astemperature. In an exemplary embodiment, the aircraft is a verticaltakeoff and landing aircraft. In an exemplary embodiment, the rotor isan anti-torque rotor.

An exemplary method includes communicating a condition of an electricmotor to a pilot during flight of an aircraft wherein the electric motoris driving a rotor and communicating to the pilot a “time availablevalue” before the motor reaches a critical condition limit. In anexemplary embodiment, the aircraft is a vertical takeoff and landingaircraft. In an exemplary embodiment, the rotor is an anti-torque rotor.

This summary is provided to introduce a selection of concepts that arefurther described below in the detailed description. This summary is notintended to identify key or essential features of the claimed subjectmatter, nor is it intended to be used as an aid in limiting the scope ofclaimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with standard practice in the industry, variousfeatures are not drawn to scale. In fact, the dimensions of variousfeatures may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates a vertical takeoff and landing aircraft according toone or more aspects of the disclosure.

FIG. 2 illustrates another vertical takeoff and landing aircraftaccording to one or more aspects of the disclosure.

FIG. 3 schematically illustrates an aircraft incorporating a peak poweruse pilot monitoring system according to one or more aspects of thedisclosure.

FIG. 4 illustrates an example instrument display at a first time instantaccording to one or more aspects of the disclosure.

FIG. 5 illustrates an example instrument display at a second timeinstant according to one or more aspects of the disclosure.

FIG. 6 illustrates an example instrument display at a third time instantaccording to one or more aspects of the disclosure.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof various illustrative embodiments. Specific examples of components andarrangements are described below to simplify the disclosure. These are,of course, merely examples and are not intended to be limiting. Forexample, a figure may illustrate an exemplary embodiment with multiplefeatures or combinations of features that are not required in one ormore other embodiments and thus a figure may disclose one or moreembodiments that have fewer features or a different combination offeatures than the illustrated embodiment. Therefore, combinations offeatures disclosed in the following detailed description may not benecessary to practice the teachings in the broadest sense and areinstead merely to describe particularly representative examples. Inaddition, the disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Conditional language used herein, such as, among others, “can,” “might,”“may,” “e.g.,” and the like, unless specifically stated otherwise, orotherwise understood within the context as used, is generally intendedto convey that certain embodiments include, while other embodiments donot include, certain features, elements and/or states. Thus, suchconditional language is not generally intended to imply that features,elements and/or states are in any way required for one or moreembodiments or that one or more embodiments necessarily include suchelements or features.

In the specification, reference may be made to the spatial relationshipsbetween various components and to the spatial orientation of variousaspects of components as the devices are depicted in the attacheddrawings. However, as will be recognized by those skilled in the artafter a complete reading of the present application, the devices,members, apparatuses, etc. described herein may be positioned in anydesired orientation. Thus, the use of terms such as “inboard,”“outboard, “above,” “below,” “upper,” “lower,” or other like terms todescribe a spatial relationship between various components or todescribe the spatial orientation of aspects of such components should beunderstood to describe a relative relationship between the components ora spatial orientation of aspects of such components, respectively, asthe device described herein may be oriented in any desired direction. Asused herein, the terms “connect,” “connection,” “connected,” “inconnection with,” and “connecting” may be used to mean in directconnection with or in connection with via one or more elements.Similarly, the terms “couple,” “coupling,” and “coupled” may be used tomean directly coupled or coupled via one or more elements.

FIG. 1 illustrates an exemplary vertical takeoff and landing (VTOL)aircraft 10 incorporating an electric power monitoring system 5according to an embodiment of the disclosure. VTOL aircraft 10 includesa rotor system 12, a fuselage 14, a landing gear 16, and an empennage18. Rotor system 12 may rotate blades 20. Rotor system 12 may include acontrol system for selectively controlling the pitch of each blade 20 tocontrol direction, thrust, and lift of aircraft 10. Fuselage 14represents the body of aircraft 10 and may be coupled to rotor system 12such that rotor system 12 and blades 20 move fuselage 14 through theair. Landing gear 16 supports aircraft 10 when aircraft 10 is landingand/or when aircraft 10 is at rest on the ground. Empennage 18represents the tail section of the aircraft and may feature componentsof rotor system 12 and anti-torque rotor 20′, illustrated as tail rotorblades 20′. Anti-torque rotor 20′ may provide thrust in the samedirection as the rotation of blades 20 to counter the torque effectcreated by rotor system 12 and blades 20. Teachings of certainembodiments recognize that tail rotor blades 20′ may represent oneexample of an anti-torque rotor; other examples may include, but are notlimited to, tail propellers, ducted tail rotors, and ducted fans mountedinside and/or outside the aircraft. The anti-torque system may includetwo or more anti-torque rotors 20′, such as in an electric distributedanti-torque system.

Teachings of certain embodiments relating to rotor systems describedherein may apply to rotor system 12 and/or other rotor systems, such asother tiltrotor and helicopter rotor systems. The rotor system mayinclude an electric powered push propeller. It should be appreciatedthat teachings from system 5 may apply to aircraft other than VTOLaircraft 10, such as airplanes and unmanned aircraft, to name a fewexamples.

In accordance to an exemplary embodiment, VTOL aircraft 10 incorporatesa hybrid propulsion system 22 including a combustion engine 24 and anelectric propulsion system 26. In accordance with some embodiments,propulsion system 22 may be an all-electric system suitable for examplefor flights of limited duration.

In the illustrated example, combustion engine 24 is mechanicallyconnected to a transmission 28 and transmission 28 is mechanicallyconnected to blades 20 through mast 30. In accordance to an embodiment,electric propulsion system 26 includes an electric motor 32 mechanicallyconnected to anti-torque rotor 20′, a generator 34 coupled to combustionengine 24 and electric motor 32, and a controller 36 operable to receivesensor data and communicate the sensor data to a pilot. In accordancewith one or more embodiments, the controller may determine and orcalculate an electric propulsion system 26 condition. Controller 36 maybe included in the flight computer, a component of the flight computer,and/or in communication with the flight computer. Electrical propulsionsystem 26 may include one or more batteries 38. Controller 36 may detectelectrical propulsion system 26 conditions and in real-time determine acondition parameter, e.g., a control limit, and communicate indicatorsof the condition parameter to the pilot. The condition parameter(s) maybe communicated to the pilot in the fuselage via visual displays,audible alerts, and/or physical cueing.

For ease of description, some of the required systems and devicesoperably associated with the present control system are not shown, i.e.,sensors, connectors, power sources, mounting supports, circuitry,software, and so forth, in order to clearly depict the novel features ofthe system. However, it should be understood that the system is operablyassociated with these and other required systems and devices foroperation, as conventionally known in the art, although not shown in thedrawings.

FIG. 2 illustrates another exemplary VTOL aircraft 10 incorporating anelectric power monitoring system 5. Electric propulsion system 26 inthis embodiment includes a first electric motor 32 to drive anti-torquerotor 20′ and a second electric motor 40 operatively connected to mast30 to drive blades 20. Controller 36 is operable to receive sensor datafrom electric propulsion system 26, in particular, electric motors 32,40, to determine a propulsion system condition and communicate acondition parameter to the pilot. The condition parameter(s) may becommunicated to the pilot via visual displays, audible alerts, and/orphysical cueing.

In the FIG. 2 example, combustion engine 24 is used to power generator34 and to recharge batteries 38. Combustion engine 24 is notmechanically coupled to rotor system 12 in the illustrated embodiment.Generator 34 is shown connected directly to combustion engine 24although it may be connected through a transmission. Combustion engine24 may be a smaller and a lighter-weight engine than utilized in atraditional aircraft and it may be operated at idle during a significantportion of flight operations. The weight of aircraft 10 may besignificantly reduced relative to a traditional VTOL aircraft by using alighter-weight combustion engine, less onboard fuel quantity, removal ofa transmission or use of a reduced sized transmission, and removal ofthe anti-torque drive shaft.

Electrical propulsion systems are desirable to minimize noise, conserveenergy, reduce pollution, and reduce operating costs. Effectiveutilization of electrical propulsion systems depends on minimizingweight. The electric motors must be designed and selected to providesufficient power for safe flight. Electrical motors often have a peakpower rating up to about two times the continuous power rating forlimited time durations. Although some motors may have a high peak tocontinuous performance capability, the duration of the peak performancecapability is typically limited by heat buildup.

More power is typically required during takeoff and hovering than in anyother flight regime. Once the aircraft is in cruise mode the electricalpower requirement is significantly reduced. The limited duration highpower requirement of the VTOL aircraft permits selecting a smaller,lighter-weight, motor having a continuous power rating sufficient tomeet the normal operating conditions and peak power capability that issufficient to meet the short-duration high power conditions such asvertical take-off, hovering, and vertical landing. A multi-motorvertical lift aircraft may be designed to utilize peak (limited timeduration) motor performance in the event that one or more of the motorsfail. For example, if the remaining operable motors can operate at about60 to 80 percent above their continuous power rating for a limitedduration of time, for example, 5 to 10 minutes, the aircraft can landsafely, or get to a lower (continuous power) flight condition withoutrisk to damaging the still-operable motor(s).

To ensure safe operation, the pilot must be made aware if the remainingoperable electric propulsion system 26 is operating above a continuouslimit, up to the peak power condition, and the pilot must be made awareof the time available to operate at those limits. Based on the conditionof the electric motor, typically temperature, the pilot can determine ifa high power task, such as a vertical landing, can be performed orcompleted within the time available limit. For example, if aircraft 10has been performing in high power conditions, such as repeated hoveringand/or right sideward flight or crosswinds, it may be necessary for thepilot to maneuver into a lower power flight regime so that the electricmotor can cool to a temperature that will permit temporary operation atthe higher (peak power) condition for a short time.

FIG. 3 is a schematic illustration of an exemplary embodiment of anelectric power monitoring system 5 incorporated in an aircraft 110.Aircraft 110 may be a VTOL aircraft. Aircraft 110 includes an electricpropulsion system 150 driving a rotor 152. Rotor 152 may be a main rotor(e.g., proprotor), an anti-torque rotor, or a push propeller or fan. Ananti-torque rotor may include for example rotor blades, tail propellers,ducted tail rotors, and ducted fans mounted inside and/or outside theaircraft. A push propeller may be utilized for example to provide aforward thrust in a cruise or transitional mode. Electric propulsionsystem 150 includes an electric power source 154 and an electric motor156. Aircraft 110 may include two or more electric motors 156. Electricpower source 154 may include a generator and/or batteries.

Electric power monitoring system 5 includes a controller 158electronically connected to motor 156 and an instrument 160 tocommunicate one or more electric motor conditions to the pilot ofaircraft 110. Instrument 160 may convey one or more electric motorconditions visually, audibly, and or by physical cueing. The visualinterface may use graphical, textual, and numerical elements and thevisual interface may flash, change color, change content, appear,disappear, move or change location, or otherwise change in response tothe state of the electric motor 156. Instrument 160 may be located inthe fuselage 14 (FIG. 1) of the aircraft. In an unmanned aircraft 110,the electric motor condition may be configured to provide the instrumentinformation to a remote pilot of the aircraft through telemetry. If theunmanned aircraft does not require a remote pilot, then the electricmotor condition information may be processed directly by the aircraftsystem flying the unmanned aircraft.

Electric power monitoring system 5 includes one or more sensorsconfigured to conduct measurements, such as and without limitation,ambient air temperature, altimeter, electric motor winding temperature,rotor torque, motor power, motor electric current, and generator load.FIG. 3 illustrates an electric motor temperature sensor 162, an ambientair temperature sensor 164, an altitude pressure sensor 166, and asensor 167 for measuring other conditions.

FIGS. 4 to 6 illustrate an example of an instrument 160 of an electricpower monitoring system at different points in time. With additionalreference to FIG. 3, electric power monitoring system 5, determines amargin between a motor condition measurement and a motor condition limitat multiple time instances during the duration. The duration may be, forexample, during flight of the aircraft or while the electric propulsionsystem is energized. The margin is the difference between the measuredmotor condition and the motor condition limit. A pilot alert may beinitiated when the margin reaches a determined trigger limit and thepilot may be provided with an indication that permits him to determinehow much time he can remain in the “above continuous power” flightcondition without damaging the remaining good motor. In the illustratedexamples, the electric power monitoring system is based on thetemperature of the electric motor.

The windings of motor 156 will reach thermal equilibrium while operatingwithin the motor's continuous duty capability. The temperature of motor156 will increase as the power demand on motor 156 increases. When motor156 is operating a peak power, the motor has a certain rate oftemperature rise. The motor may fail when the temperature of the motorwindings increases to a certain level. If the motor winding temperatureis maintained below the continuous limit, the windings can cool off, andthe motor can again be powered up to supply peak power for a limitedtime. The electric power monitoring system 5 alerts the pilot when amotor trigger limit is reached and a limited duration of time isavailable at the present motor power level before the motor damagetemperature limit is reached. In this example, the time available valueis associated with a temperature margin. The time available value may bedecremented, visually and or audibly, so that the pilot can take timelyremedial action to put the aircraft in a lower power required condition.For example, if a pilot is about to take on a sling load, the electricpower monitoring system 5 can identify whether a sufficient length oftime is available to complete the task. Electric power monitoring system5 may continue to monitor motor conditions, power demand, and ambientconditions to revise the remaining time available value. It may be aparticular desire to alert the pilot of a reduction in the anticipatedtime available value.

Instrument 160 depicted in FIGS. 4-6 is a composite displaycommunicating electric motor information in multiple formats. Instrument160 is a visual display and may include a speaker 160′ and or a physicaldevice 160″. Examples of physical device 160″ include withoutlimitation, pedals, control stick, collective control, and cycliccontrol, stick. For the purpose of description, FIGS. 4-6 show motorconditions in terms of temperature and includes numeric valuesrepresenting example motor conditions. The electric power monitoringsystem is not limited to communicating the motor conditions intemperature or to the example numeric values. The numeric value of themotor condition limit and the associated motor trigger limit may bebased, for example, on electric motor catalog data, motor nameplatedata, testing data, and or proprietary data associated with the use of aparticular electric motor with a particular aircraft.

Instrument 160 includes a graphical display 168 of the motor 156 windingtemperature measured by sensor 162. In this example, graphical display168 is a bar display having a first region 170 illustrating temperaturerise extending to a motor condition limit 172. Other forms of thegraphical display may be presented, including without limitation acircular graphical display. Motor condition limit 172 may be shown invarious manners, for example as an end point on graphical display 168,by a mark such as a line or an arrowhead, and or by a numeric value. Inthe illustrated example, motor condition limit 172 is communicated by aline and textually with a numeric value, e.g. “180.”

The graphical display includes a motor condition region 174 representingthe real-time motor condition reading, obtained in this example bytemperature sensor 162. In accordance to an embodiment, motor conditionregion 174 may vary in color depending on the value of the motorcondition reading relative to the motor condition limit. Instrument 160may also include a motor condition identifier 176, textually showing themotor condition reading, e.g. “146° C.” in FIG. 4.

Electric power monitoring system 5 includes a motor trigger limit 178,which may be shown on graphical display 168 in various manners, forexample by a mark such as a line or an arrowhead, text, and or a colorchange on the graphical display. In the illustrated example, motortrigger limit 178 is depicted on graphical display 168 by a mark andtextually with a numeric value, e.g. “165.” Motor trigger limit 178 is anumeric value that identifies that the motor condition, e.g. motortemperature, is approaching the motor condition limit 172. Motor triggerlimit 178 may be utilized by controller 158 and not directlycommunicated by instrument 160. Motor trigger limit 178 may be selectedin various manners. For example, motor trigger limit 178 may bepredetermined, prior to flight, to provide a desired initial durationfor the time available at peak power from which to initiate a countdown.According to one or more embodiments, motor trigger limit 178 may beactively determined during the flight to provide a desired initial timeavailable value at peak power. For example, the in-flight monitoring ofmotor 156 may indicate that the temperature rise of motor 156 isaccelerating faster than estimated by the preflight motor data andcontroller 158 may reduce motor trigger limit 178 so that the initialtime available value is at a desired value such as, and withoutlimitation, three, five, seven, or ten minutes.

Region 180 of graphical display 168 between motor condition limit 172and motor trigger limit 178 is a critical available motor conditionmargin. Available motor condition region 180 may be emphasized, whenmotor trigger limit 178 has been reached, by a color change, flashing,and/or other mechanisms such as an audible alert via speaker 160′ orphysical cueing, for example, vibration, of physical device 160″.Instrument 160 may include a countdown timer 182 that shows theestimated time available value associated with available motor conditionmargin 180. Countdown timer 182 may periodically adjust to show theestimated time available value or continuously decrement. In addition toalerts via graphical display 168 and countdown timer 182, an audiblesignal such as “5 minutes of Peak Power Available” may be announced whenmotor trigger limit 178 is reached.

An example of operation of an aircraft 110 and an electric powermonitoring system 5 is now described with reference to FIGS. 1-6. Withreference to FIG. 4, the aircraft is in a cruise flight regime andelectric motor 156 is operating within its continuous power rating. Thelogic in controller 158 is continuously reading the windings of motor156 in real-time and communicating the real-time motor condition to thepilot via instrument 160. In FIG. 4, the real-time motor temperature isshown by motor condition region 174 of graphical display 168communicating the motor temperature relative to motor condition limit172. In the illustrated exemplary instrument 160, motor conditionidentifier 176 numerically communicates the value of the real-time motorcondition. In this example, countdown timer 182 is blank indicating thatmotor 156 is not operating above motor trigger limit 178. In someembodiments, countdown timer 182 may display a numeric value, such asthe initial countdown value, prior to the motor condition reaching motortrigger limit 178.

FIG. 5 illustrates instrument 160 at a second time instant when thetemperature of motor 156 reaches motor trigger limit 178. Motorcondition region 174 shows that the real-time motor temperature is atmotor trigger limit 178 and motor condition identifier 176 numericallycommunicates the value of the measured motor temperature. In thisexample, countdown timer 182 turns on when the motor temperature reachesmotor trigger limit 178 to provide an alert to the pilot. If countdowntimer 182 was on prior to meeting motor trigger limit 178 it may beginto flash and or change color to communicate to the pilot that motortrigger limit 178 has been reached. In this example, countdown timer 182is initiated at five minutes, however, it is noted that the countdowntimer may be initiated at a different value greater or less than fiveminutes.

FIG. 6 illustrates instrument 160 at a third time instant as the motorcondition trends beyond motor trigger limit 178 and approaches motorcondition limit 172 as shown by motor condition region 174 on graphicaldisplay 168. Countdown timer 182 decrements toward 0:00 as the motorcondition approaches motor condition limit 172.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the disclosure.Those skilled in the art should appreciate that they may readily use thedisclosure as a basis for designing or modifying other processes andstructures for carrying out the same purposes and/or achieving the sameadvantages of the embodiments introduced herein. Those skilled in theart should also realize that such equivalent constructions do not departfrom the spirit and scope of the disclosure and that they may makevarious changes, substitutions, and alterations without departing fromthe spirit and scope of the disclosure. The scope of the inventionshould be determined only by the language of the claims that follow. Theterm “comprising” within the claims is intended to mean “including atleast” such that the recited listing of elements in a claim are an opengroup. The terms “a,” “an” and other singular terms are intended toinclude the plural forms thereof unless specifically excluded.

1-20. (canceled)
 21. An aircraft, comprising: an electric propulsionsystem comprising a motor coupled to a rotor; and a controller connectedto the electric propulsion system to monitor a rate of temperaturechange of the motor, to determine an estimated time available before thetemperature will reach a high-temperature limit, and to communicate theestimated time available.
 22. The aircraft of claim 21, furthercomprising an instrument to visually communicate the estimated timeavailable.
 23. The aircraft of claim 21, further comprising aninstrument to audibly communicate the estimated time available.
 24. Theaircraft of claim 21, further comprising a first instrument to visuallycommunicate the estimated time available; and a second instrument toaudibly communicate the estimated time available.
 25. The aircraft ofclaim 21, wherein the rotor is an anti-torque rotor.
 26. The aircraft ofclaim 21, wherein the rotor is an anti-torque rotor: the electricpropulsion system comprises a generator; and further comprising aninstrument to visually or audibly communicate the estimated timeavailable.
 27. A method, comprising: monitoring, during flight of anaircraft, a motor temperature and a rate of motor temperature change ofan electric motor that is driving a rotor; determining, based on therate of motor temperature change, an estimated time available until themotor temperature reaches a high-temperature limit; and communicatingthe estimated time available.
 28. The method of claim 27, furthercomprising initiating communicating the estimated time available whenthe motor temperature exceeds a trigger limit.
 29. The method of claim27, wherein the communicating the estimated time available comprisesvisually displaying a countdown timer.
 30. The method of claim 27,wherein the communicating the estimated time available comprises audiblycommunicating.
 31. The method of claim 27, further comprising initiatingcommunicating the estimated time available when the motor temperaturemeets a trigger limit, wherein the trigger limit is a time value. 32.The method of claim 31, comprising communicating the estimated timeavailable to a pilot as a countdown timer.
 33. The method of claim 32,further comprising adjusting the countdown timer in response to a changein the rate of motor temperature change.
 34. The method of claim 27,further comprising initiating communicating the estimated time availablewhen the motor temperature meets a trigger limit and the motortemperature is increasing, wherein the trigger limit is a time value.35. The method of claim 34, comprising communicating the estimated timeavailable to a pilot as a countdown timer.
 36. The method of claim 35,wherein the countdown timer is a visual display.
 37. The method of claim35, comprising communicating the estimated time available to a pilotaudibly.
 38. The method of claim 27, wherein the aircraft is ahelicopter and the rotor is an anti-torque rotor.
 39. The method ofclaim 38, further comprising initiating communicating the estimated timeavailable when the motor temperature meets a trigger limit and the motortemperature is increasing, wherein the trigger limit is a time value.40. The method of claim 39, further comprising communicating theestimated time available to a pilot as a countdown timer; and adjustingthe countdown timer in response to a change in the rate of motortemperature change.